View Full Version : My Rotor Blade & Power Situation
04-09-2007, 03:43 PM
OK, here's where I stand.......
When building my EA81 powered 2 place SxS Air Command, I decided to buy SC blades. After alot of Phone calls & discussion with Jim V., We decided that 28' x 8.5" blades were what I needed for my planned gross weight of 1100 lbs.
I paid alot of money & waited a long time for them. When I recieved them I was very happy with everything about them !
The bad thing is ...my climb performance is poor ! Of course more thrust could solve this.
Before swapping out my engine for a much heavier one I decided to try a set of Dragon Wings.
Ernie B. was nice enough to bring a set for me to try/buy at ROC 2005(I think). After flying Shar & I with the SC blades there(struggling for altitude) we swapped them out with the 28' DW's.
The performance with these much lighter blades was Identical. So I bought them! I also purchased, from another vendor there, a used 1' & a 5' DW hub bar. Now, against Ernie's recommendations , I could have 3 different blade lengths...25', 28' & 29' .
During my test flights back home, while I was trying to optimize engine & prop, other problems arose. Nosewheel & engine problems have now been corrected.
I am now back to trying to optimize rotor blades to maybe make up for lack of power ?
As soon as the temps get better around here, I will be back at it. :wacko:
To be continued shortly......
04-09-2007, 03:56 PM
OK, I'm back.
Of course I'm always thinking about trying other props for more thrust but I just want to see what bigger blades will get me.
So, after some test flying with 2 60lb cement bags I will then try to make my 28' DW's into 29' DW's with the 5' hub bar.
If they seem safe , I will proceed with performance testing.
Many knowledgeable people have suggested longer blades while others say it will not help! I plan to find out !
This is what I would like to discuss here...... Dinner's ready !
04-09-2007, 04:52 PM
OK , done eating.
We should all know how to size blades according to weight , but what is the best blade loading ?
I have read that Ernie B. does not recommend any less than 1.3lbs/sqft.
If my calculations are right...1100lbs with 28' blades would be...1.78
1100lbs with 29' blades would be...1.66
1100lbs with 30' blades would be...1.55
So could I not use 30' blades safely ?
So why do some tell me it takes more power to spin bigger blades ?
Yet they say the bigger blades offer more float. Isn't float = to lift ?
Unfortunately, I can't trade my SC's for a bigger set so the best I can do right now is try the 29' DW's.
Many years ago when my brothers & I bought our AC's (mine a 447 with 23' blades & theirs a 532 with 25' blades) I took theirs up for a spin.
Well the 532 definitely was more powerful but the amount of lift was much greater. Even when chopping the throttle to descend the thing did not want to come down! More float(lift)
Too bad I never tried the 25' blades on my 447. Pretty much the same scenario !
I'll leave it at that for now......please feel free to add to this topic.
04-09-2007, 05:00 PM
just make sure that the blades are not to long, and hit the ground. just my 2 cents
04-09-2007, 05:46 PM
CLS-- the bottom line is that you flat dont have enough power --an EA 81 is HP limited --if your getting 110 HP -- you will still be marginal @ 1100#. Thirty foot blades will help but the performance will still be only slightly better than marginal.
I just sold my DW's as I didnt find that they offered any performance gains over the Fleck/Vortec/Rotorhawks that I had been using --I went back to the Fleck/Vortec/Rotorhawk extrusions --in my case they work better--
I have a single place EA81 powered gyro that weighs in at 820# . The engine puts out 100 HP and my disc dia is 27 ft -performance is adequate--
One question if the performance of the DW's and Sport Copter Blades were IDENTICLE --why did you buy them --especially if they offered no clear improvement ?
A Blade loading of about 1.5 and 120HP or more is necessary to get decent performance --but even then you will have to watch the DA or you wont like the performance--
Im building a Tandem 2 placer --I'll be using a 150hhp modified 2.2 Soob -- my MAX loading will be 1.65 --normally I will be at 1.5 so 150hp and a 31 ft disc will work well for me--
Good luck in your quest ----but get MORE power !!
04-09-2007, 05:55 PM
Geeze Man why are these gyro's so fat? What does an EA81 weigh?
I am not criticizing, Just that the Gyro I helped John Stevens build was a 2 place dominator with a 618 weighed in at 401lb empty, plenty of power.
So even if you had a 200 lb engine plus extra framework bracing you should be around 600Lb, So is the subie that heavy?
04-09-2007, 06:54 PM
My gyro weighs 820 # AUW --thats EVERYTHING including Pilot and Full load of Fuel --
04-10-2007, 03:03 AM
Dave, Blades that could hit the ground was one of my first concerns. After testing the machine for a while now, I am sure that I could use 30' blades with no contact very easily. This is no longer a concern.
Mike & Scott, I believe the EA81 engine to be around 200lbs plus accessories. I'm told the EJ series are well over 300lbs.
I don't have a dyno, so my prop has to be the method of power measurement. It is a 68" 3 blade Warp Drive, just like almost every 2.2 equipped RAF uses but with a different hub. That being said.... It is right now set at exactly 11* at the tips. My redrive ratio is 2.18- 1.
Static full power runups get me to 5400 RPM's. 13* setting will only get me to 5000 RPM's..... about 200 rpm's / degree of pitch.
I believe that most 2.2 RAF's have their tips set at 12* at the tip to get 5250 RPM's. Their belt drive ratios are a little different.
The point is ....not that big of a difference for a much heavier engine.
Now for the weight issues....I am going to verify the weight of my machine again this year but earlier tests have given me 704 with 10 gallons of fuel & the 86 lb SC blades. So add 400lbs for pilot & passenger....= 1104 lbs
My mast is 3 2x1 construction & the motor mount is very heavy duty.
I am always looking for places to trim weight but they just seem so trivial right now. If I could shave 20lbs it might be worth it.
It is hard to believe that the RAF with all of it's 2x4 construction , a cabin with doors, dashboard, heater, 23 gallon tank, EJ22, & trim setup, is less than 200 lbs more.
If you need 1lb of thrust for every 2lbs of weight the RAF would never leave the ground.....but it has 30' blades. I would love to see some thrust #'s from them.
Oh & Mike ...why did I buy the DW blades? I guess because of their value & they were easier to horse around on the ground & spin up due to their lighter weight. I am glad I did because with the bigger hub bar, I will be able to try 29' blades without spending any more moola !
04-10-2007, 03:25 AM
Oh & by the way.....with just one person & no "bags", the climb performance is fantastic!
Adding another 100lbs is very noticable. So with bigger blades, a more efficient prop, & a little bit of weight savings, I believe(I hope) that the machine will perform quite well.
If not...I see an EJ25 with fuel injection & an Autoflight redrive in my not so distant future. But I will have to sell this EA81 setup to fund the swap !
04-10-2007, 05:13 AM
Chris--it looks like your getting the max power available out of the EA81. Your right about the weight 200# is pretty close to the average EA81. Im getting pretty close to the same RPM with similiar pitch settings on my Warp Drive 68" prop. I pull about 425# of static thrust.
A 2.2 or a 2,5 will pull a LOT more thrust --somewhere in the neighborhood of 600#'s+. Either of these engines will top the scales at 300# set up and ready to fly --but they are smooth and RELIABLE!
I think you can achieve what you want with 30 blades with your current set up -it wont be a barn burner but it will fly pretty well --good luck--
04-10-2007, 05:38 AM
I pulled 470 lbs several times & that was before the RAM dual port heads & intake.
I don't think the 81 can do much more than that without FI & a supercharger but I won't go there...$$$
I'd sure like to try an IVO & a Prince prop, just to see if I can get more!
The best RAF pull that I witnessed was Gary Neal's at ROC...that was .I believe 560lbs . I think that cabin causes low numbers , staticly.
Hopefully we will get alot of comparitive numbers at BD's .
I will be sure to post my findings !
04-10-2007, 09:49 AM
Chris-- It looks like your putting out about 115-120 HP --pretty good for an EA81--your best bet may be to go to a larger prop --this will give you extra thrust (on the cheap). Looking at your pictures it seems possible to go to a 72" prop with minimal changes. I know this will affect your thrust line but it shopuldnt hurt to much --use the Sport Copter Blades and the extra weight should offset the thrust line change---
I rebuilt my EA81 last year hoping to get more power--I got some but not enough --so Im going to do it again this summer -- bigger bore -higher compression /more off the heads --rework the ignition-- Im also going to bump my prop diameter up 2" to 70" --I have the room and it will still clear the keel with no problems--
04-10-2007, 02:06 PM
In my humble opinion........
Quit spending money on improving an engine that can't produce the power to get the amount of lift you want. Or buying rotors. neither will help you.
Just put your money into a new engine.
If you do.....you can use the 29 footers and get the best performance.
It sounds harsh but there is no replacement for displacement.
The "float" in rotors is different from "lift" because they are different performance characteristics. It doesnt take power to decend. It takes gobs of power to climb.
04-10-2007, 08:38 PM
A Rotax 914 puts out over 100 HP with less than 100 CI --a Continential O-200 puts out 100 HP with about 200 CI --my old 7.3 Litre (444CI ) Diesel truck put out less HP an Torque than my new 6.0 Litre (365 ci) Diesel does --so increased displacement does not necessairly relate to increased HP.
But I gotta agree thaat a 2.5 Soob will do the job!
That reminds me I have a low time (less than 120 hrs SMOH ) O-200 sitting in my hanger --I wonder if it is a "-C" (pusher config)
04-11-2007, 03:48 AM
You mentioned above that…
(I just sold my DW's as I didnt find that they offered any performance gains over the Fleck/Vortec/Rotorhawks that I had been using --I went back to the Fleck/Vortec/Rotorhawk extrusions --in my case they work better—
In the beginning I thought it was a joke Mike, but NO WAY FLECK/VORTEC orRotorhawk are better that DW. There are of course no magic rotorblades but as I mentioned many times here before, the fiber Mc Cutchens are superior to all other metal blades.
I have much experience with all above mentioned rotorblades . Yes, in your case maybe they work better.
04-17-2007, 07:47 AM
Anybody learn anything at BDs to add to this ?
How does the EA81 powered dominator perform ?
05-07-2007, 02:34 AM
What would be a good teeter bolt/tower height for 29' DW's ?
1100lb gross weight ?
05-09-2007, 01:51 PM
5/8" bolt is what I use.
05-14-2007, 04:09 PM
Brent, what are YOU talking about ?
05-16-2007, 12:26 AM
You need this, no just pulling your leg! But we use 2.4 to 1 gear ratio on 70 / 72" warp drives ( SUB4 at around 118HP ) 28' RFD blades. The problem with " no substitute for cubes " is weight. Best to run a smaller engine faster and trade rev's for torque. HP is a function of cylinder pressure and combustion frequency ie rpm's, so to make more power use more rev's but use a cylinderhead that will allow good breathing at higher rpm ( bigger bang's and more of them! ). I am supprised that the RAM performance heads don't do better, maybe there is another problem, manifold or ignition timing or type of cam, possibly exhaust problems? many factors, is it EFI? You will generaly add five to eight HP on a SUB4 engine by using a tuned induction with proper tapers and flared bellmouths, coupled with EFI.
Incidently this Autoflight engine you see here has tapered inlet tubes leeding to flared bellmouths one and a half times the dia. inside the plenium chamber. Attached is a picture of an earlier type of tuned SUB4 inlet, approx 130HP. Don't be fooled, yes the 2.5 is a good engine, but heavy! The EA series engines have a lot going for them ( with proper heads! )
Well, I said it
05-16-2007, 01:53 AM
Neil, thanks. Believe me, I am watching !
Some good news & bad.... If I go with this engine, I would not need one of your gearboxes. My Souza redrive from my EA81 would fit the EA82....Right?
I would hate to have to add another 100lb of engine(2.2 or 2.5).
Are you reading my progress under the Air Command section ?
I have a 38 Weber carb on the way to replace the 32/36.
The Ram engine has now given me a thrust pull of 520lbs. I now have 29' DW blades on her & things are looking better!
I believe she needs more fuel.
Keep watching for more news!
05-16-2007, 02:11 AM
Yes sorry, I'm so last year, I see all my questions answered in S and S. You will see some correspondence from me under that heading. Actually I'm just as happy not to sell anything here as it's probably not realy the place to be doing that, although I do think Autoflight has some good stuff ( I had to say that). Top priority is to see Subaru conversions work and be seen to work effectively. Don't take what I said about your carburator too much too heart, I just don't like them.
05-16-2007, 02:26 AM
No problem at all......I just glad that someone, at this time of day, shows some interest.
I couldn't ask for a better person to be chatting with.
The bellhousing & crank bolt pattern on the EA82.....Is it identical to the EA81 ?
Are the mounting lugs on the block the same ?
05-16-2007, 03:24 AM
Well it would seem yes and no. The Autoflight EA series gearbox will fit both EA81 and 82, but the 82 has 10mm crank bolts and the 81 are 9mm. All I do is manufacture all flywheel drive plates at 9mm and when a gearbox is ordered for an 82, I drill it out. The engine mounts look the same but in fact are not, with the width being the same ( at 303mm ). The length apart is in the order of 10mm shorter. All my Dominators are made now to suit the 82 short block. Yes Souza's gearbox will fit the EA82, that was hard to write!Attualy I'm not sure now, how does he fit the gearbox to the bellhousing, I see it's modified. Autoflight one fits to standard unmodified unit. I'm sure it could be made to fit.
05-16-2007, 03:47 AM
"Actually", thats better. Would you post a picture of the way the gearbox is mounted to your engine when you get a chance, now I'm interested. I distrusted aftermarket EFI units for years, ( ignorant ). But after being forced to use them with the SUB4 project, I've learned to respect them for what they can do. New Zealand made Link unit does fuel and ignition, turbo or no. Altitude compensating and seem immensly reliable, totally tunable. Ernie uses them, infact the picture attached is one of Ernies EJ 2.0 engines he's been using with a Link wired up.
05-16-2007, 03:58 AM
I don't know how much detail you are after, but here are some pics of it.
05-16-2007, 04:04 AM
Yes I see, thanks. Your gearbox will fit straight on to an EA82. Ron makes a nice job of those heads doesn't he.
05-16-2007, 04:07 AM
Is that inlet manifold aluminium or a coated steel?
05-16-2007, 04:44 AM
It is aluminum.
Thanks for the suggestions, Neil. Have a good day & best of luck with the new engine. I'll be keeping my eye on it !
05-16-2007, 05:13 AM
520 lbs of thrust..... how much more could you want out of it? That is more than the 100 horsepower Rotax 912S powered machines pull.
05-16-2007, 05:24 AM
I don't see why it is not flying OK it has the thrust. With 520 a 1040 gyro should fly OK.
05-16-2007, 10:48 PM
Thats more than a Rotax 912S can deliver, I should think so!
Your quest for more fuel and air for your engine has me questioning the holley carb on my EA81.
While cruising the web, I found this general information on carburetor sizing according to CFM for 4 stroke engines. This should be the minimum CFM, then find the carb with the correct air/fuel mixture throughout the rpm range.
For 4 stroke carb engines:
CFM needed = ((engine size in cubic inches) x (maximum RPM) / 3456) x VE%
VE = volume efficiency of the air/fuel ingested by the engine, 75% is normal for most engines and race engines are capable of near 100% efficiency.
05-20-2007, 09:41 PM
Its no good strapn on more horses if you dont have a prop that will make good use of them.
Either a bigger diameter or wider chord prop will supprise you how much more thrust you can get from your EA81.
Bigger rotor blades dose make a difference too, but all your HP and rotor money is waisted if you cant transfer your HP to thrust efficiantly.
Iv seen a relitivly light single place enclosed machine, with 200+HP JUST fly.
The 6BL prop made more noise than thrust.
05-21-2007, 03:58 AM
Birdy: You made a good point about having a wider chord on the blades.
My Ivoprop has a much wider chord than the Warpdrive blades that were on it. Here are two pictures showing the comparison between the two.
Not counting being able to adjust the pitch...it just looks to me that the wider blades would transfer more HP to the air.
I had a picture of each blade along side each other but cant find it in my computer. Its hard to judge between these two pics.
05-23-2007, 04:11 PM
Stan, I,m planning on switching out my WD prop on my 2.5 RAF for the in flight adjustable Ivo like you have. Did you go with a three blade? I'm planning on the magnum model. I understand the Ivo is much quieter in cruise at the lower rpm. What are the noise levels on T/O if your turning 5150 rpm as with the WD? I,m thinking that if the tip speed is the same the noise level will be about the same? Thanks for your help.
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